Towards a process-structure model for Ti-6Al-4V during additive manufacturing

This paper presents the development of an integrated approach for microstructure prediction in laser beam powder bed fusion (PBF-LB) manufacturing of Ti-6Al-4V, primarily focused on the solidification morphology and solid-state phase transformation. A finite element (FE) model of the PBF-LB process is developed for prediction of thermal history and spatial distributions of temperature. Based on the relationships between FE predicted thermal history, thermal gradient and key manufacturing parameters such as laser power and scanning speed, an additive manufacturing (AM) process map for different solidification morphologies, including columnar-to-equiaxed transition, is developed. Phase transformation kinetics for the non-isothermal steps is adopted and implemented within a stand-alone code based on the FE predicted thermal histories of sample material points. The method is successfully validated by comparison with published experimental data and the developed process-structure model can be potentially used as a process design tool to efficiently produce tailored and optimized microstructures for specific applications.